Intensity fluctuations of a laser beam reflected by a rough surface in atmospheric turbulence

A model of the log-amplitude covariance function of a Gaussian beam propagating through the atmospheric turbulence is proposed based on the Rytov Method. The intensity correlation function of the reflected field from a rough surface is analyzed with the extended Huygens-Fresnel principle. The covariance and variance and residual scintillation index of the received intensity are calculated for the cases of a collimated beam and a focused beam. It is found that the effect of the log-amplitude covariance of the turbulence along the forward path plays a large role in the intensity fluctuation of the received wave. The size of the laser spot on the target has an “aperture effect” on the covariance and variance of the received intensity.